CERN Accelerating science

ATLAS Note
Report number	ATL-PHYS-PROC-2018-072
Title	Electromagnetic processes with Quasireal photons in Pb+Pb collisions: QED, QCD, and the QGP
Author(s)	Steinberg, Peter (Brookhaven National Laboratory (BNL))
Corporate Author(s)	The ATLAS collaboration
Collaboration	ATLAS Collaboration
Publication	2019
Imprint	15 Jul 2018
Number of pages	4
In:	Nucl. Phys. A 982 (2019) pp.259-262
In:	The 27th International Conference on Ultrarelativistic Nucleus-Nucleus Collisions, Venice, Italy, 13 - 19 May 2018, pp.259-262
DOI	10.1016/j.nuclphysa.2018.10.087
Subject category	Particle Physics - Experiment
Accelerator/Facility, Experiment	CERN LHC ; ATLAS
Free keywords	QCD ; MCGENERATORS ; HEAVYIONS ; EGAMMA ; MUCOMBINED
Abstract	Electromagnetic processes, both photon-photon and photon-nucleus, are shown to be useful in studying aspects of QED, QCD, and potentially the QGP. Using lead-lead collisions at $\sqrt{s_{NN}}$=5.02TeV , the ATLAS detector has performed measurements of exclusive dimuon production, light-by-light scattering (via exclusive diphoton production), and photo-nuclear dijet production. These are all important examples of ultraperipheral collisions, where the nuclei do not interact hadronically. A recent study of the opening angles of dimuons produced in hadronic heavy-ion collisions, after subtracting heavy-flavor backgrounds, demonstrates that the dimuons carry information correlated with the overlap geometry, potentially about the density of charges in the QGP itself.
Copyright/License	publication: © 2018 Published by Elsevier B.V. (License: CC-BY-NC-ND-4.0)

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